Hydraulic power lift



Nov.vl 7, 1942- a M CORMICK ETAL 2,302,537

HYDRAULIC POWER LIFT Filed April 19, 1937 '3 Sheets-Sheet 1 Elrrr mlerrnc Cormack y er" m Hansen Ml ATTORNEYS Nov. 17, 1942. E, McCORMl K ET AL 2,302,637

HYDRAUL I C POWER LIFT Filed April 19, 1937 3 Sheets-Sheet 2 m zo' INVENTORS 1 Elmer Mc Cormick 20,8 BY rl n Hansen I fi fl/fiww M FIG 1B A TTORNE ys Patented Nov. 17, 1942 UNITED STATE nrnnauuc rowan ur'r Elmer McCormick and Merlin Hansen, Waterloo,

Iowa, assignors to John Deere Tractor Company, Waterloo, Iowa, a corporation of Iowa Application April 19, 1937, Serial No. 137,651

9 Claims. (01. 137-439) The present invention relates to hydraulic mechanisms, and more particularly to improvements in hydraulic mechanisms for tractors aod the like for use as power lift mechanism therefor.

Hydraulic power lift mechanism of this general type is illustrated and described in the application of Elmer McCormick, Milford D. Stewart, and Wayne H. Worthington, Serial No. 749,706, filed October 24, 1934, now United States Patent No. 2,107,760, issued February 8, 1938, and the present invention relates to modifications and improvements in such mechanism.

The principal object of the present invention is the provision of improved control means for the hydraulic mechanism whereby it is unnecessary for the operator to hold the control lever or foot pedal down for any given length of time during the raising or lowering cycle. In this connectlon, the present invention contemplates the provision of such control means that once the foot pedal is pressed down sufliciently to start the raising or lowering operation, the pedal may be released and the mechanism will complete its cycle of operation. The pedal may be pressed down as rapidly or as slowly as the operator dee sires, or it may be held down indefinitely without interfering with the normal operation of the mechanism. In the present construction, also, if

the foot pedal is released before it ispressed down sufficiently to start the raising or lowering operation, the entire mechanism will return to the position it occupied before the foot pedal was actuated, and the raising or' lowering operation will not be completed.

Another object of the invention is the proviquickly adjust the power lift so that the rate of movement of the actuating piston thereof in the from the reservoir to the bearing compartment for the power take-off shaft bearing which is positioned beneath the reservoir, and to provide a sump at one side of said bearing compartment sion of improved means whereby the operator can into whichgrit and metal particles picked up by 5 the oil may settle, whereby such foreign matter will be prevented from entering the bearing compartment below the reservoir.

A still further object of the present invention is the provision of an overload release valve so positioned that access may be had to the valve from the outside of the power lift casing, thereby making it unnecessary to remove such casin for that purpose.

Other objects and advantageous features of the present invention will be apparent from the following description of the preferred embodiment of our inventiontaken in connection with the accompanying drawings, in which-- Figure 1 is a vertical longitudinal section taken through the rear end of a tractor in which the present invention has been embodied; Figure 1 corresponding to a section taken along the line t-l of Figure 2;

Figure 2 is a rear view, looking forwardly, of the construction illustrated in Figure l, with certain parts of the casing members being shown in section in order to better illustrate the operating mechanism;

Figure 3 is a vertical section taken along the line 33 of Figure 2 showing the controlling valve mechanism in the position corresponding to the lowered position of the apparatus;

ure 4 is a section similar to that illustrated in Figure 3, and showing the controlling valve mechanism in the position to which it is moved in the raising operation;

Figure 5 is a section similar to that illustrate in Figures 3 and 4, and showing the controlling valve mechanism in the position corresponding gto the hydraulically locked raised position of the apparatus;

Figure 6 is a fragmentary horizontal section taken along the lines 6-8 of Figures 1 and 2,

and showing the valve means for regulating the return flow of the fluid from the cylinder;

Figure 7 is a vertical section taken along the line of Figure 2, and showing the stop means for the valve actuating mechanism and the means for releasing said stop means;

Figure 8 is a fragmentary vertical section taken along the line 8-8 of Figure 1, and showing the means for automatically returning the rock shaft to lowered position when the power lift has been actuated to return to such position;

Figure 9 is a longitudinal section taken alon the line 9-9 of Figure 3, and showing the overload release valve between the pressure channel the line llil of Figure 2, and showing the means for supplying oil to one of the power takeoff shaft bearings; and

Figure 11 is a vertical section taken along the line H--|l of Figure 1, and illustrating the several integral cam elements of the controlling valve mechanism.

Referring now to the drawings, as shown in Figure 1, the reference numeral I indicates the rear portion of a combined crank case and supporting framework of a tractor of well known construction, and 2 indicates the rear axle housing of such a tractor, such rear axle housing in the present case being of the banjo type. Such axle housings comprise laterally directed housing extensions (not shown) in each of which a drive shaft 3 is journaled by any suitable means.

Each of said drive shafts 3, one of which 'shown in Figure l, carries a large driving gear 4, said gears being actuated by suitable transmission mechanism and differential means which are indicated as an entirety by the reference numeral 5.

While our improved hydraulic power lift has been illustrated in connection with and mounted on a farm tractor in view of the fact that certain features of our invention are more particularly concerned with providing improved power lift apparatus for such tractors, it is to be understood, of course, that in its broader aspects our invention is not to be limited to such association, and may be applied in any other situation to which it is applicable.

In its preferred form our hydraulic power lift mechanism comprises a unit that is adapted to be bolted over the rear opening 6 of the axle housing 2, and includes a central housing 1 that is adapted to be secured, as by bolts 8, over such rear opening 6 in lieu of the usual cover plate that covers such opening in tractors of the above mentioned type. The central housing 1 includes a forward wall ll provided in its upper portion with an opening l2, and a cylinder i3 is secured Over this opening and extends forwardly substantially into the body of the tractor between the driving gears 4 above mentioned. The forward end of the cylinder I3 is closed, and its rear end is flanged as shown at 14 and secured by bolts I5 over the opening 12 in the central housing 1. Slidably mounted within the cylinder i3 is a piston I6 provided with suitable sealing means H by which it is rendered leak-tight within said cylinder. I

As shown in Figure 2, the upper portion of the central housing 1 is provided with right and left hand laterallyv extending integral housings or sleeve members 2!, said members being provided with suitable bearing means in which a lifting rock shaft 23 is mounted for rockin movement. The central portion of the rock shaft 23 carries an arm 24 that is fixed thereto in any suitable manner, and arranged to extend in a generally downward direction within the central housing 1. The outer end of the arm 24 carries a pin 25, and a pair of pitman straps 26 serve to connect said pin with a wrist pin 21 carried by the piston 5- adjacent the forward end thereof. By this means, therefore, the piston i6 is operatively connected with the rock shaft 23 so that when the piston is forced'outwardly of the cylinder 13, or to the left as viewed in Figure l, the rock shaft 23 is rocked in a clockwise direction. The rock shaft 23 is provided with squared ends 29 to receive lifting arms (not shown) whereby said rock shaft may be connected by any suitable lifting connections with implements or other operating units associated with the tractor.

The piston 16 is operated by pressure derived from a hydraulic pump of the positive displacement type. The pump is indicated in its entirety by the reference numeral 3|, and as shown in Figures 1 and 2 it comprises a suitable housing 32 that is carried by and secured to the rear wall 33 of the central housing 1 by bolts 34. A pair of steel dowel pins 35 carried at opposite ends of the housing 32 and adapted to be inserted in openings provided therefor in the rear wall of the central housing 1 serve to aline the holes for the bolts 34 in the housing 32 and the central housing 1 in the assembling operation. The pump gears are indicated by 31 and 38, the gear 31 being journaled on a bearing 39 supported on a short shaft 46 disposed in sockets 4i and 42 formed in the pump housing casting 32 and in the rear wall 33 of the power lift housing 1. The other pump gear: 38 is provided with three keyways or slots 43 (Figures 1 and 2) in one of which a key 44 (Figure 2) is placed for securing the gear 38 to a power takeoff shaft 46- which extends forwardly into the tractor body I and is operatively connected with the tractor motor by any suitable means. The purpose of providing the additional slots 43 will be explained later herein. The shaft 46 extends rearwardly longitudinally of the tractor between the two main driving gears 4 and through an opening 41 in the rear wall 33 of the power lift housing 1 (Figure l) and is journaled in a bearing 48 supported by the pump housing 32. A cap 6| is provided for closing the opening that receives the bearing 48, and the rear end of the power take-off shaft 46 extends through said cap and is sealed by suitable bushing means 52. A sealing washer 50 is also provided between the cap 6| and the shaft 46 on the inner side of the bushing 52. The rear end of the shaft 46 is splined, as shown at 53, to receive suitable power take-oil connections by which any operating unit or units may be driven by the rotation of said shaft.

The pump gears 31 and 38 are rotatedin the direction of the arrows in Figure 2 by the rotation of the shaft 46, and such rotation of the gears builds up pressure in one side of the pump housing 32 and creates a suction in the other side of the housing. On the suction side of the pump housing the rear wall 33 of the power lift housing 1 is provided with an opening 55 (Figure 2), and a similar opening 56 is provided on the other side of the pump housing 32 at the pressure side of the pump 3|. The opening 55 affords communication between the suction side of the pump and the lower portion of thehousing 1, which forms a reservoir R for the hydraulic fluid, and the opening 66 leads into a vertically disposed pressure channel 51 formed in a thickened section 53 at the rear wall 33, as best shown in Figures 1 and 6. In Figure 2 the vertical pressure channel 51 is indicated in dotted lines, and the upper terminal end 59 thereof (Figure 6) communicates with an opening 6| in the valve housing 62 that contains the valve mechanism for controlling the power lift mechanism. The opening 6i communicates with an upwardly curving passageway or pressure chamber 63 (see Figures 3 and 9) formed in the valve housing 62 and which will be referred to later.

In the central portion of the housing 1 a section 64 extends from the rear wall 33 to the front wall I l thereof and is provided with an interior chanthe cylinder l3.

nel or bore 65 leading from a registering opening 66 (Figures 1 and 6) formed in the valve housing the cylinder casting l3, and the channel 68 leads forwardly and into the closed end of the cylinder l3, as best shown in Figure 1.

The valve housing 62 encloses all of the valve parts and associated controlling mechanism, as best shown in Figures 1 and 2, and this valve mechanism is arranged to control the flow of fluid between the pressure conduit 51 and the channels 65 and 68 communicating with the closed end of As best shown in Figures 2 and 6, the valve housing 62 also includes a lower chamber 69 that is separated from the upper chamber 63 by a wall H! (see Figures 2 and 4), and communicates through the opening 66 above described with the channel 65. The upper portion of the lower chamber 69 communicates with the upper chamber or curved passageway 63 through a valve opening II that is controlled by a valve 12. As above described, the liquid under: pressure from the pump 3| is forced'upwardly through the pressure channel 51 and through the opening 6| into the upper pressure chamber or curved passageway 63, and if the valve 12 is open, the liquid will pass through the opening ll into the chamber 69 and around through the opening or port 66 into the bore 65, whence the liquid passes through the channel 68 into the closed end of the cylinder l3.

The upper pressure chamber 63 is extended upwardly to form a chamber section 13 (see Figures 3 to' and pominunicates through an-opening 16 with the space 16 above the wall forming the upper portion of the pressure chamber 63, which space 76 has direct communication with the upper portion of the reservoir R as shown in Figure 2.

The valve 12 is fixedly mounted on a stem 8| which passes through a bushing 62 in the section forming the upper wall of the chamber 63, and at its upper end the valve stem carries a sleeve 83 which is of generally cylindrical fonnation and is slidable in a cylindrical opening 85 formed in the section 66 of the valve housing 62 that forms the upper wall of the upper chamber section 13. The sleeve 83 is of the same diameter as the diameter of the opening above mentioned,

so that said sleeve serves as a valve closure for such opening, as will appear later, and the stem II is of such a length as to permit the valve 72 to move well toward its full open position before the sleeve or plunger 83 approaches the opening 15.

The entire unit, comprising the valves 72 and 63, may be shifted to'three different positions. Figure 3 shows the position in which the valve 12 is opened asmall amount, but the valve 83 is caused to remain substantially in its wide open position. Since this latter valve is still in its wide open position, no pressure is developed by the pump since the liquid in the pressure chamber 63 merely discharges back into the reservoir B through the opening 15. However, since the valve 12 is now open, the liquid within the closed end of the cylinder l3 may escape by flowing backwardly or rearwardly through the channels 68 and 65 into the chamber 69 and up past the valve 12 and through the Opening H into the ervoir R through the opening 15. Thus, the opening of the valve 12 relieves any pressure within the cylinder l3 occasioned by any reaction of the load acting against the piston through the rock shaft 23 and the arm 24. The above mentioned positions of the valves 12 and 83 are those to which they are moved when the rock shaft isto be rocked to lower the implements, as

- uid forced upwardly through the pressure channel 51 into the pressure chamber or curved passageway 63 passes downwardly through the opening ll and into the chamber 69, from whence the liquid flows under pressure through the passageway 66 into the channels and 68 and into the closed end of the cylinder I3. Since the valve 83 is closed, direct communication between the pump and the reservoir is cut off, and the pressure developed by the pump is all imposed on the piston I6, with the result that it moves from its position shown in Figure 1 and swings the arm 24 connected with the rock shaft in a clockwise direction to thereby rock the rock shaft to raise the implements connected with said rock shaft.

The third position of the valve unit is illustrated in Figure 5, and is the position to which said. parts are moved when the raising of the implements has been accomplished, and in which position of the parts the fluid is trapped so as to hold the implements in such raised position.

When in this third position, the valve 12 is closed, which prevents the pressure in the pressure chamber or passageway 63, communicated thereto through the channel. 51 from the pump 3|, from entering into the chamber 69 and into the cylinder l3. In this position of the valve means, however, the cylindrical valve 83 is open, thus leaving the opening 15 unobstructed so that the liquid under pressure being delivered to the chamber 63 from the pump may pass therefrom through the upper chamber section 13 thereof and .out through the opening 15 back into the reservoir R. It will be seen, therefore, that in this position of the valve unit the pump will run free and no pressure will be transmitted to the cylinder l3. It will also be noted that any liquid that is trapped in the closed end of the cylinder I3 is held therein by the closing of the valve 12, since the opening II is the only means by which the liquid in the closed end of the cylinder I3 can escape. Thus, the piston I6 is held hydraulically locked in the position it occupies when the valve 12 is closed. Suitable means, which will be described later, has been provided by which the movement of the piston l6 toward its left hand limit, as viewed in Figure 1, automatically shifts the valve means from the position shown in Figure 4 to the position shown in Figure 5.

The means for controlling the valve mechanism is indicated in its entirety by the reference numeral 9| and will now be described. This means includes a cam member 92 mounted in the upper portion of the valve housing 62 and adapted to shown in Figure 3, then applying pressure to the chamber 63, whence it is discharged into the respiston |6 by shifting the valve means to the position shown in Figure 4 to cause the pressure of the pump to force the piston outwardly, and then, lastly, shifting the valve means to the position shown in Figure 5 for hydraulically locking the piston in its outer position.

The valve unit comprising the valve members 12 and 83 is biased for movement toward the position shown in Figure 5 by a spring 04 which is disposed in the chamber 09. This spring 34is seated in a plug 95 which is provided with a suitable recess for receiving the lower end of the valve spring 94 and is threaded into an opening in the lower portion of the valve housing 02 as best shown in Figures 2 to 5. The valve operating cam 92 bears upon the top of the cylindrical valve plunger 03' of the exhaust port 15, and said cam has a section of maximum throw, indicated by the reference numeral 90, that engages the valve member 83 when the power lift is raising, as shown in Figure 4. At' the end of the raising stroke the cam is automatically turned through a comparatively small angle, as will be hereinafter described, allowing the valve to be forced upwardly by the spring 94 against a cam section 91 of minimum throw, as shown in Figure 5. From this position the 'cam 92 is turned approximately 180 to the position shown in Figure 3, causing the power lift to lower. When in this latter position the valve 12 is opened, thereby permitting the oil from the cylinder to pass backwardly as above described and escape through the port 1I. With the parts in this position the port 15 is also open so that the fluid from the pump entering the passageway or pres sure chamber 03 will also escape through the port 15 into the reservoir R.

The cam member 92, together with several other cams to be mentioned later, is formed as an integral part of a casting IOI, as best shown in Figure 11, said casting being journaled for rotation on a rock shaft I02 supported in bearings I03, I04 in the upper portion of the power lift housing 62 as shown in Figure 2. The rock shaft I02 is provided with a crank arm I05 at one end (Figure 2) which is connected by a link I to a trip lever or foot pedal I01 fixed to one end of a shaft I08 that is journaled in a pair of lugs I09 formed integral with or fixedly secured to the sleeve members 2I at the upper portion of the central housing section 1. Suitable packing means 98 held in position by a spring 00 (Figure 2) seals the rock shaft I02 in the valve housing 62., At the opposite end of the shaft I00 is fixed a second trip lever or foot pedal I01 whereby the link I00 may be actuated by operating either of said levers I01 or I01, as will be readily understood. A coiled torsion spring IIO supported on the shaft I08 between'the lugs I00 has one end hooked over the foot pedal I01 and its opposite end in engagement with the left hand lug I09 as viewed in Figure 2, said spring acting to immediately return the foot pedals I01 and I01 to their normal positions and to swing the crank arm I downwardly to the position shown in Figure 2, after the operators foot has been re- 1 moved therefrom after depressing the same to member I I4 clamped to the cam shaft I02 as best shown in Figure 11. The pawlJII is biased, as by a spring IIS, for engagement with a ratchet wheel IIG (see Figure 1) that is formed integral with the cam assembly IOI (Figure 11). The foot pedal, linkage, and ratchet mechanism are so designed that for each operation of the pedal to its extreme down position the cam assembly will be rotated approximately 180, but, as will hereinafter appear, it is not necessary that the foot pedal be depressed to its extreme down position as means have been provided to move the cam assembly after the foot pedal has been depressed to a predetermined point. It will be noted also, in this connection, that the ratchet wheel H0 is provided with four notches II1 spaced apart as shown in Figure 1, and the purpose of providing the two additional notches will be explained later.

As best shown in Figure 11, the cam assembly IOI also includes a power cam I2I provided-with two sections I22 and I23 of minimum radius spaced apart, and also with two other sections I24 and I25 of maximum radius also spaced 180 apart. This power cam is engaged by a cam following roller I26 which is joumaled on one end of an arm I21 fixedly connected at its opposite end to a hub I20 rotatably supported on a shaft I29 suitably journaled in bearing portions I3I formed integral with the housing 02 as shown in Figure 2. A second arm I33 formed integral with the hub member I20 extends upwardly from the latter and is provided at its outer end with a spring abutment I34. A coiled compression spring I30 having one end disposed over a lug I36 on the spring abutment I34 and its other end disposed over a lug I31 (Figure 3) on an integral portion I30 of the housing 02 reacts against the housing portion I30 and exerts a force against the abutment I34 to force the roller I20 against the cam I2I. In the extreme raised and lowered positions of the power lift, the roller I20 is at rest in one of the low points I22, I23 on the cam I2I as shown in Figures 3 and 5. When, however, the cam assembly IN is rotated by the foot pedal mechanism, the roller I20 is forced outwardly by the cam I2I against the compression of the spring I30 until such roller passes one of the high points I24, I20 of the. cam. Thus in moving from the position shown in Figure 3, which is the position when the implements are lowered, to a position which will cause the power lift to raise the implements, as shown in Figure 4, the roller I20 passes from the low point I22 over the high point I24 of the cam, after which the compression of the spring I30, acting through the roller I20, is sufficient to rotate the cam I2I and the entire cam assembly formed integral therewith into the position shown in Figure 4, at which point the rotation of the cam assembly is interrupted by a third cam I that is formed integral with said cam assembly and is best i1- lustrated in Figure 7.

The cam I is provided with an abutment I42 between the high and low points thereon which is adapted to abut against the outer end of a stop arm I43 fixed to or formed integral with a hub member I44 journaled on the shaft I20 that supports the hub member I20 before mentioned. This stop arm I43 is yieldingly urged into a position to abut the cam I4I by a compression spring I45 acting against a second arm I40 fixed to the hub member I44 and ex tending downwardly therefrom, said spring reacting against the rear wall of the housing 62, as shown in Figure 7. The positions of the several parts as shown in Figure 7 correspond to the positions of the parts shown in Figure 4 in which the valve mechanism is set for raising the power lift.

When the piston I6, which is connected to the actuating arm 24 on the power lift rock shaft 23 as above described, nears the'end of its travel in the raising operation, that is toward the left as viewed in Figures 1 and 7, the lower end of the arm 24 engages a pin I48 that is slidable longitudinally in an opening I49 extending through a lug II fixed to or formed as an integral part of the housing 62. As the piston completes its stroke the pin I48 is moved against the lower end of the arm I 46 and rotates said am against the action of the spring I45 in a clockwise direction. As both the arm I46 and the stop arm I43 are fixed to the hub I44 this movement of the arm I46 moves the stop arm I 43 also in a clockwise direction and out of engagement with the abutment I42 on the cam I. It will be noted in this connection that in Figure 4 the roller I26 has not quite reached the low point I23 of the cam I2I, and the reason for this is that the rotation of the cam assembly was interrupted by the stop arm I43 engaging the abutment I42 on the cam I as above described. However,

when the stop arm I43 is'disengaged from the abutment I42 when the piston I6 reaches the end of its stroke in the raising operation, the pressure of the rollei I 26 against the/cam I 2| will rotate the entire cam assembly from the position shown in Figure 4 to the position shown in Figure 5, where it is held by the roller I 26 resting In the low point I23 of the cam I 2I When the parts are in the position shown in Figure 5 the implements connected with the rock shaft 23 are in raised position as has been above described. The pin I48 also acts to prevent any accidental excessive amount of rearward movement of the piston I6, whereby the arm 24 might be jammed foot pedal in either the raising or the lowering operation the operator should release the pedal before it has been depressed far enough to move the high point I24 or I25 of the cam I2I past the roller I26, the pressure of the roller against the cam will force the cam assembly back into the normal position that it had previously occupied before the foot pedal was depressed, with the roller I26 at rest in one of the lowpoints I22 or I23 of the cam, which would result in the implements remaining in a raised or lowered position, and it would be necessary for the operator anism will be in the into the valve control mechanism, as the headed forward end I48'- of the pin contacts the lug I6I in the rearward movement of the pin and absolutely limits the rearward movement of the-piston, as will be readily understood. 1

Now, if it is desired to lower the implements,

either trip lever III! or I81 is again depressed to rotate the cam assembly to move the high point I25 of the cam I2I past the roller I26, and it can then be released immediately, as the cam assembly will continue to be rotated by the power of the spring I35 until the roller I26 comes to rest in the low point I22 of the cam I 2I which brings th parts into the position shown in Figure 3 which is the lowered position of the implements.

It will be seen from the foregoing, therefore, that by providing the power cam I2I which is automatically moved by the cam roller I26 after the ratchet wheel I I6 has been moved by actuation of the trip lever to rotate the "entire cam assembly to move either high point I24 or I 25 of the power cam past the cam roller, the cam roller I26 will act to automatically move the cam I2I until the cam roller comes to rest in either lowpoint I22 or I23 of the power cam I2I. Thus it will be seen that it is only necessary that the trip lever be depressed sufficiently to rotate the cam assembly through slightly more than 90, after which the power cam I2I will act to move the entire cam assembly through the remainder of its movement. If, however, in actuating the to again depress the trip lever in order to raise or lower the implements.

As above mentioned, the ratchet wheel II6 has been provided with four notches II'I spaced apart, although two oppositely disposed notches would be sufficient for an operative structure, and the purpose of providing the additional intermediate notches will now be pointed out. If, after the operator depresses the foot pedal to rotate the cam assembly, such assembly should stick before it has completed its cycle, as may occur if the oil is so still that the power cam I2I has insuflicient capacity to rotate the cam through the remaining portion of its stroke, the operator will naturally again depress the foot pedal. Upon this second depression of the pedal the dog II I will engage in the intermediate notch and assist the power cam in moving the cam assembly to its final position.

While it is believed that the operation of the valve mechanism and the means for actuating the same in the raising and lowering operations will be apparent from the foregoing description thereof, it is thought best to briefly describe the same. Assuming that the control mechanism has previously been operated to lower the implements, and the rock shaft and piston have been moved to the position shown in Figure 1, the valve mechposition shown in Figure 3, and the cam ro11e3gI26 will be at rest in the low point I22 01' the power cam I2I. Now if the trip lever III! is depressed, the arm I I3 will be rocked and the ratchet dog III will shift the ratchet wheel I I6 and the entire cam assembly formed integral with said wheel through approximate- 1y The curve of the valve cam 92 is such that the high point 96 thereof has moved the valve unit downwardly, against the tension of the spring 94, sufllciently to completely close the valve 83 and completely open the valve 12 as shown in Figure 4. No oil can now escape back to the reservoir and all of it is forced through the opening 1| and into the chamber 69 and the channels 65 and 68, toward the closed end of the cylinder I 3. This forces the piston I6 toward the left in the cylinder I3, which, by reason of the connection of the pitman straps 26 with the lower end of the rock shaft actuating arm 24, causes the rock shaft 23 to be rocked and the implements or other load connected therewith to be lifted. In this operation the cam MI is also rotated through approximately 180 into the position shown in Figure 7, in which position the spring controlled arm I43 comes into engagement with the abutment I 42 on the cam I 4|, and momentarily arrests-the movement of the cam assembly. As the piston I6 nears the end of its raising movement, the lower end of the rock shaft actuating arm 24 strikes the pin I48 which in turn moves the arm I46, against the action of the spring I45, toward the left as viewed in Figure 7, swinging the arm I43 formed integral with the arm I46 out of engagement with the locking the cam. Upon unlocking of the cam III the cam roller I26 under the action of the spring I35 will force the power cam -I2I to rotate until the roller I26 comes to rest in the low point I23 of the power cam as shown in Figure 5. This movement of the power cam I2I rotates the valve cam 92 sufficiently to move its high point 96 off of the top of the valve 83 and bring the low point 91 of said cam 92 over the top of the valve 83, at which time the valve unit is moved upwardly under the action of the valve spring 94 to bring the top of the valve 83 into contact with the low point 91 of the cam 92 as shown in Figure 5. This movement of the valve unit opens the valve 83 and completely closes the valve I2. When the parts are in this last mentioned position the oil between the valve I2 and the piston is trapped and hydraulically locks the lift mechanism in a raised position, and the. pump is caused to discharge directly into the reservoir R through the opening I5. To lower the implements theoperator again. depresses the trip lever sufficiently to rotate the cam assembly until the cam roller I26 rides over the high point I25 on the power cam IZI, and the cam roller I26 under the action of the spring I35 then forces the power cam to move the entire cam assembl again into the position shown in Figure 3, which opens the valve I2 slightly and breaks the hydraulic lock, permitting the implements to move to lowered position. In this position of the parts the valve 83 is also open and the pump runs free.

As above mentioned, the hydraulic power lift mechanism of the present invention is adapted to be used in connection with farm tractors for raising and lowering implements or other parts that are carried by the tractor, and such implements, as is well known in the art comprise various kinds. some of which are light in weight while others are relatively heavy. While it is desirable that light implements, such as cultivators, be dropped quickly, it is very important that heavy implements, such as listers, planters, etc., be dropped more slowly on account of the danger of damage to the tools, and, therefore, in the present construction means have been provided whereby the speed of lowering of the implements connected with the rock shaft 23 may be regulated, and this is accomplished by adjusting the limit of closure of the valve 81 which registers with the port 36 he= tween the chamber 69 and the bore or channel 85, which parts have been before referred to. As best shown in Figures 1 and 6, the valve 61 is forced toward a closed position by a compression spring IBI having one end seated in a recess I82 formed in the housing section 84 and its opposite end engaging the valve. On the side opposite the spring IBI the valve is provided with a relatively long valve stem I63 that extends through an opening provided therefor in the bottom wall I84 of the housing 62. The opening through which the valve stem I63 extends is enlarged and interiorly threaded adjacent its outer end as shown at I65 to receive a set screw I66 that engages the outer end of the valve stem. The set screw is adapted to be locked in any adjusted position by a lock nut I61, and a protecting cap I68 is provided for the outer end of the set screw I66. By this construction, when the oil is being forced under pressure through the opening 66 and into the cylinder as above described to actuate the power lift to raise the implements, the oil forces the valve 61, against the compression of the spring IBI, to its extreme open position in con abutment I42 on the cam Ill and thereby untact with the edge I69 of the spring recess, allowing free passage of the oil irrespective of the setting of the screw I66. During the return move-.- ment of the piston I8, however, the oil-flows back to the valve-61 as has been before described, and the combined pressure of the oil and the spring ISI acting against the valve 61, returns it to its closed position, as limited by the set screw I66. It will thus be apparent that by adjusting the valve by means of the set screw I66, the rate of return flow of the oil from the piston I6 can be adjusted over a wide range, thus adjusting the rate of speed of the return of the piston to the position it occupies when the implements are in lowered position.

In the present construction means have been provided for insuring the return of the power lift rock shaft 23 to lowered position regardless of whether or not there is an implement attached to the rock shaft, and this means is shown in Figure 8 and will now be described. This means comprises a helical spring I8I that is disposed around the rock shaft 23 within one of the laterally extending sleeve members 2I of the power lift housing I. One end of this spring is attached to a pin I82 fixed on the rock shaft 23 while the opposite end of the spring is anchored in a bushing I 83 which is screw threaded into the outer end of the sleeve member 2| and is rigidly held in position by bolts I84. This bushing I83 also acts as an outer bearing for the rock shaft 23 within the sleeve member 2|. By this construction, when the hydraulic mechanism is actuated to rock the rock shaft to a position corresponding to the raised position of the implements the spring is stressed by such rocking movement, and when the hydraulic mechanism is actuated to return the parts to a position corresponding to the lowered position of the implements the spring I8I will operate to return the rock shaft to such position.

Suitable overload release mechanism has been provided, and in the present construction such mechanism is readily accessible from outside of the power lift housing, so that it is not necessary to remove the casing to obtain access to the valve. The location of this safety valve is best shown in Figures 1 and 9 and is positioned near the rear of the control housing 62. This valve is indicated by the reference numeral I! and normally closes a passage I92 between the chamber 63 and the top portion of thereservoir R. The valve I9I is held closed by a heavy coiled spring I93 that bears at one end against the valve I9I and at its other end against a stud bolt I94. By this construction, whenever the pressure in the pressure channel 51 and in the chamber 63 exceeds a certain'maximum, the valve I9I will be forced open against the action of the spring I93 and permits the oil in the chamber 63 to escape through the passage I92 into the reservoir R. Access may readily be had to the safety valve I! by merely removing the stud bolt I94 and withdrawing the spring I93 through the bolt hole.

A sump 2IJI is provided at the bottom of the reservoir R as shown in dotted lines in Figure 2 and in plan section in Figure 10. This sump 2M is disposed at one side of a compartment 202 that is provided in the power lift housing to receive the power take-oft shaft 46 before described. The bottom of the sump 20I is provided with a drain 203 that is closed by a plug 204. By this construction, by removing the plug 204 and allowing a portion of the fluid to flow from the reservoir, any particles of grit or metal collected in the sump can bedrained oif without the necessity of draining of! all of the oil from the reserlubricated by oil leaking along the sides of the gears 31 and 38 from the high pressure side of g the pump, and in order to prevent the oil pressure in the bearing housing from building up to a point where leakage through the rear seal 50, 52 would take place, the extra keyways or slots 43 before mentioned have been provided in the gear 38 of the pump that is fixed to the power take-ofi shaft in'order to conduct the oil from the bearing housing through the gear and into the compartment 202 (Figure 1) from which it fiows through an opening 201 (Figure into the sump 20!. At the forward end of the compartment 202 as viewed in Figure 1, we provide a second bearing support for the power take-off shaft 46 which is in the form of a sleeve 208, and this bearing sleeve is lubricated by oil from the axle housing 2 of the tractor, the oil flowing through a small opening 2 at the rear end of the bearing sleeve 208 and working through the bearing in a groove 2i2 provided in the power take-oil shaft 56 as best shown in Figure 10. A sealing washer 213 held in place by a helical spring 214 surrounding the shaft 46 prevents the escape of the oil from the power lift pump into the axle housing 2,

Oil is inserted into the hydraulic unit through an opening 22! in the top of the, casing 82 as shown in Figure 2, said opening being normally closed by a plug 222 threaded into the opening. This plug 222 is provided with a small boring (not shown) extending therethrough to provide a breather for the hydraulic unit. The unit is filled with oil up to the level of a plug 223 (Figure 2) threaded into an opening on the right side of the valve housing 62.

While we have shown and described above the preferred structure in which the principles of the present invention have been embodied, it is to be understood that our invention is not to be limited to the specific details shown and described above, but that, in fact, widely difierent means may be employed in the practice of the broader aspects of our invention.

We claim:

1. Control means for hydraulic mechanism having interconnected valve means for controlling the fiow of fluid through said mechanism, comprising, in combination, a cam adapted to be advanced to move said valve means into successive positions, a trip lever, means for advancing said cam by actuation of said trip lever to move said valve means to one position, disengageable means for locking said cam after it has advanced to move said valve means into said one position, and means for automatically ad vancing said cam after it is unlocked for moving said valve means into a second position.

2. Control means for hydraulic I mechanism having interconnected valve means for controlling the flow of fluid through said mechanism, comprising a cam adapted to be advanced to move said valve means into successive positions, a trip lever, means for advancing said cam by actuation of said trip lever, means for automatically advancing said cam after said trip lever has advanced said cam beyond a predetermined point, to move said valve means to one position, means for locking said cam after it has advanced to move said valve means into said one position, and

means for unlocking said cam, said automatic advancing means operating to advance said cam after it is unlocked for moving said valve means into a second position.

8. Control means for hydraulic mechanism having valve means for controlling the fiow of fiuid through said mechanism, comprising a rock shaft, a unidirectionally rotatable cam journaled on said rock shaft and adapted to be advanced to move said valve means successively between open and closed positions, means on said rock shaft for advancing said cam' upon rocking of said shaft, a trip lever for rocking said rock shaft, a

' power cam fixed to said first cam and disposed coaxial with said rock shaft, and means for advancing said power cam to move said first cam after said trip lever has advanced said first cam beyond a predetermined point to move said valve means to one position comprising an arm pivotally mounted adjacent said rock shaft and swingable into engagement with said power cam, and a spring biasing said arm into engagement therewith.

4. Control means for hydraulic mechanism having valve means for controlling the fiow of fluid through said mechanism, comprising a rock shaft, a cam journaled on said rock shaft and adapted to be unidirectionally advanced to move said valve means successively between open and closed positions, a ratchet wheel fixed to said cam, a trip lever for rocking said rock shaft, a pawl carried by said rock shaft and engaging said ratchet wheel whereby said cam is advanced by actuation of said trip lever, a power cam disposed coaxial with said rock shaft and fixed to said first cam, an arm pivotally mounted adjacent said rock shaft, a spring applying force to said power cam through said arm for advancing the latter to move said first cam after said trip lever has advanced said first cam beyond a predetermined point to move said valve means to one position.

5. For use in hydraulic mechanism having valve means controlling the fiow of fiuid through said mechanism, the combination of a cam member operable to successively move said valve means to diiferent positions, means for advancing said I cam member to one position, a second cam member integral with said first cam member, means engageable with said second cam member for locking said cam members in said one position, means for unlocking said cam members, and automatically acting means for advancing said cam members after unlocking thereof for moving said valve means to a second position.

6. For use in hydraulic mechanism having valve means controlling the flow of fiuid through said mechanism, the combination of a cam member operable to successively move said valve means to different positions, means for advancing said cam member to one position, a second cam member integral with said first cam member, means engageable with said second cam member for locking said cam members in said one position, means for unlocking said cam members, and automatically acting means comprising a third cam member integral with said first two cam members and means for applying force to said third cam member to move the latter for advancing said cam members after unlocking thereof.

'7. Control means for hydraulic mechanism having valve means for controlling the fiow of fluid through said mechanism, comprising in combination, a cam adapted to be advanced from one position to a second position to adjust said said predetermined point, and means for arrest-- ing the movement of said first cam before it has reached said second operating position, said force applied to said second cam being effective to complete the movement of said cams after said arresting means has been disabled.

8. Control means for hydraulic mechanism having valve means for controlling the flow of fluid through said mechanism, comprising in combination, an element adapted to be moved to shift said valve means, a manually actuated con trol member engageable with said elemeiit when moved in one direction to move the element, means separate from said control member for moving said element toward a working position after said control member has moved the element beyond a predetermined point, releasable detent means for arresting the movement of said element before it reaches said working position, and

means for releasing said detent means, said element being moved to said working position by said separate means after said detent means has been released.

said rock shaft and engaging said ratchet wheel' whereby said cam is advanced by actuation of said trip lever, a power cam fixed to said first cam, a spring pressed roller applying force to said power cam for advancing the latter to move said first cam after said trip lever has advanced said first cam beyond a predetermined point to move said valve means toward a working position, releasable detent means for arresting the movement of said cam at a predetermined point before it reaches said working position, and means for releasing said detent means, said cam being moved to said working position by said spring pressed roller after said detent means has been released.

ELMER MCCORMICK.

MERLIN HANSEN. 

